Device for localizing the impact point of rays



July 14, 1959 E. DELOFFRE ET AL DEVICE FOR LOCALIZING THE IMPACT POINT OF RAYS Filed June 16, 1953 2 Sheets-Sheet 1 mvemoks'. L j ELo/ DE LOFFKE,

m wm H D E m L A z w m E July 14, 1959 L. E. DELOFFRE ET Al 2,895,057

' DEVICE FOR LOCALIZING THE IMPACT POINT OF RAYS 7 Filed June 16, 1953' 2 Sheets-Sheet 2 M X 5a 7 5G. 8

IHVEHTORS: LEor/ ELOI DELaFFfig AND EMILE Al-FR HEKRS 2,895,067 Patented July 14, 19 59 DEVICE FOR LOCALIZING rm IMPACT POINT OF RAYS Lon Eloi Deloifre, Lens, and Emile Alfred Pierre,

" a Paris, France Application June 16, 1953, Serial No. 362,120 10 Claims. (Cl. 313-95) Our invention relates to a device for ensuring the localisation of the impact point of the cathode rays upon one of the surfaces of a cathodic rays emitting system.

One object of our inventionis to provide a device for localising either the point of impact of photoelectrons on a collecting surface of a vacuum cellhavin-g parallel emitting and collecting Surfaces or of a barrier layer cell, or the impact point of thermoelectrons upon the screen of a cathodic oscillograph.

According to the invention, one of the surfaces of a cathodic ray emitting system, for instance, an electron collecting surface, such as an anode or a screen, is brought up to the suitable potential through at least two distinct points (so-called current tapping points) and has between these two points such a substantial resistance that the distribution of the electronic current between the two current tap points depends on the position of the impact point of the cathodic beam upon said surface.

Other features and advantages of the device according to the invention will appear from the following description with reference to the'accompanying drawings in which:

Fig. 1 diagrammatically shows the basic arrangement of a device having a cell with parallel emitting and collecting surfaces equipped according to the invention,

Fig. 2 is a cross section of the device illustrated in Fig. 1,

Fig. 3 is a top view of one embodiment of the anode,

Fig. 4 diagrarmnatically shows an electrical wiring using this cell,

Figs. 5 and 5a diagrammatically show, in top view, a collecting surface of such a cell, provided with four current tapping points and four current tapping lines respectively,

Fig. 6 diagrammatically shows an electrical wiring using the collecting surface of Fig. 5,

Fig. 7 diagrammatically shows a cell according to the invention provided with two deflecting elements,

Fig. 8 diagrammatically shows a modification of this cell provided with four deflecting elements,

Fig. 9 shows a cell with a transparent cathode,

Fig. 10 diagrammatically shows a cell comprising one anode associated with two cathodes,

Fig. 11 diagrammatically shows, in cross section, the anode of the cell illustrated in Fig. 10,

Fig. 12 diagrammatically shows a cell with a transparent anode provided with four current tapping points,

two of which are located on the anode and two on the cathode, and

Fig. 13 diagrammatically shows a cell having a transparent cathode with four current tapping points two of which are located on the anode and two on the cathode.

Figs. 1 and 2 illustrate the basic principle of the invention. A cathode 1 carrying a photo-emissive layer 3 is arranged facing an anode 2. This anode consists of a transparent support 4 made of any suitable material upon which a thin metallic layer 5 is deposited by means of any suitable process. According to the invention, the thickness of this layer is so thin that it is transparent and that, on the other hand, its resistivity is not negligible.

The negative pole 7 of a direct current source is connected to the cathode 1 as at 6, whereas the positive pole 8 of the same source is applied to the conductive layer 5 of the anode at two opposite points 9 and 10.

When a luminous beam is directed upon the cell according to the direction of the arrow 11, it travels through the transparent anode and strikes the cathode as in 13, which results in an emission of electrons reaching the anode layer 5 as in 12. The electrons so caught by the anode flow out through the current tapping points 9 and 10. However, as above stated, since the resistance of the conductive layer 5 is not negligible, the distribution of the current towards the points 9 and 10 will depend on the position of point 12 with respect to points 9 and 10. This fact may be used for determining the position of point 12 (or point 13) with respect to the tapping points 9 and 10 by comparing the individual currents flowing out through these points 9 and 10.

Fig. 4 diagrammatically shows a wiring using such a cell. The points 9 and 10 are connected through resistances 15 and 16 to a current source 7-8 in such a manner that the resistances formed between thepoint 12 where the electrons are caught and the tapping points 9 and 10, form two arms of a Wheatstone bridge.

In the example illustrated, it is assumed that the exciting luminous beam originates from a luminous source 17 which darts a luminous beam, through a suitable intermediate optical system 18, upon a mirror 19 adapted for rotational movement, on an axis perpendicular to the plane of the drawing, under the action of any particular phenomenon to be recorded. The luminous rays reflected by the mirror 19 get through the anode 2 as at 20 and strike the cathode 1 as at 20'. The electrons emitted are caught by the anode 2 in a zone corresponding to the point 20.

In the diagonal of the measuring bridge now appears, as at 21, a potential difference which depends on the resistance of the anode conductive layer between the points 20 and 9, on one hand and the points 20 and 10 on the other hand. This potential difference, therefore, depends from the position of points 20 relative to the points 9 and 10, i.e. from the angular position of the mirror 19.

The potential difierence available at 21 may be used, after a preliminary amplification if need be, in any conventional manner, by applying it for instance to a cathodic oscillograph, measuring apparatus, a recording apparatus, a relay, etc.

When the luminous beam is assumed to move exclusively on a straight line, the anode 2 may be in the shape of a stripe stretching over the zone where the luminous beam moves. Fig. 3 shows such an anode constituted by iostripe 14 provided with two opposite current taps 9 and Fig. 5 shows another arrangement wherein an anode 2' is provided, besides the two opposite current taps 9 and 10, with two further current taps 9' and 10' arranged on a straight line which is at right angles to the straight line determined by the taps 9 and 10. Such an arrangement makes it possible to determine the movement of a luminous beam in two directions at right angles to each other, that is to say in any direction in a surface.

In Fig. 5a, the tapping points are replaced by lines 9a, 9a, 10a, 1M1 in such a manner that any movement of the impact point in a direction parallel to .one pair of lines for instance 9a, 1011, will in no ways interfere with the electronic distribution between the lines of this P I Q I v V l 26 closed :up'oniitseifa Fig. 6 shows the use of an element such as: the one I connected in 'a'Wheatstone bridgesystem which, more I i over, comprises resistors 15 and 16,v which are pref- I I erably of the same value; whereas the tapsi9' and :10 I are connected in a second bridge system which more I "over comprises the resistors and Y16 also preferably identical with each other; The current source 7- 8 may I be common-to the-two aforesaid bridge systems. I -The position of an exciting luminous beam E relative I to the taps 9 and 10 is now determined by the potential I II difference which builds up across 21, whereas the posh 'tion of the same beam with respect. to the taps '9 and 10 I is determined by the potential difierence across: 213 1 I 1 These two potentialditferences thus make it possibie to localise theexciting beam Ezwithinthe whole area of the I anode surface 2'. r

' The operation of the device. according to. the invention may be further improved byv providing deflecting ele- I ments to concentrate the electrons on: the: anode. Fig; I l I excitin '7 shows such 'as arrangement wherein the cell which eomprises a cathode 1 and the anode 2 is further fitted with two deflectors 212 and 2310 which is applied as at i '24 ai'icl respectively a potential. whichis positive rela- I I Whereas Fig. 7 immense an with is: deflector which;

. illustrated in 'Fig; '5, in ,anelectric wiring derived from that-ofFig 4. H II comprisestwo 'currenttaps, Fig. 8 shows a cell which I 1 :coinprises a cathode land an anode 2' of the type represented in Figs; 5 and 6 fitted with ifour taps 9, 1t and I 2 9' and 10. This assembly is associated with a deflector I I is applied as at 27; I I I The 'examplesnbove-described include a transparent anode; i The device, however, may also: be realised witha transparentcathode and an opaque anode; Fig.9 shows I I I a cell which comprises .a.v cathode consisting of a trans- I i parent supporting member Ztiand a photo-emissive layer.

28', and arranged facing an opaqueanode consisting of do a conductive resistant layer 29 fitted with two opposite taps 9 and 10. An exciting beam diagrammatically represented by the arrow 30 breaks through the transparent supporting member and strikes upon the emissive layer 28' as at 30' thus giving rise to the emission of an electronic beam 31 which reaches the anode 29 in a zone 31' the location of which with respect to the taps 9 and 10 is determined in the manner explained with reference to the preceeding instances.

Fig. 10 shows a further arrangement wherein a transparent anode 34 cooperates with the two cathodes 32 and 33 arranged one on each side of the anode 34, while the cathode 32 moreover is transparent.

Fig. 11 shows a cross'section of the anode 34 which comprises a transparent supporting member 34 covered on opposite sides with transparent resisting conducting layers 35 and 36. The conducting layer 36 is fitted with two opposite taps 37 and 38 whereas the conductive layer 35 is fitted with two taps 39 and 40 located on a straight line at right angle to the line determined by the two types 37 and 38.

An exciting beam directed upon the assembly in the direction of the arrow B breaks through the transparent cathode 32 as at 32' whereby giving rise to the emission of an electronic beam which is caught by the facing conductive layer 35 and the position of which with respect to the taps 39 and 40 is determined in the manner above explained with reference to the proceeding instance. After having travelled through the transparent anode 34, the exciting beam strikes upon the second cathode 33 as at 33', which gives rise to the emission of an electronic beam caught by the anode layer 36 as in 36'. The location of the zone 36' relative to the taps 37 and 38on the layer 36 is also determined in the manner herein above explained.

nd to which a, positive potential 1 is transparentwhereasi the anode: isopaque.

I 5 Thus, this arrangement also makes it possible to determine the'position of the exciting beam according; to v I I I two directions at right angle with each other, and it also I I In this wiring, the current tapping points 9 and 10 are I 1 has the advantage of making the'circ'uits'which comprise on one hand the taps 37 and-38 and on; the; other handv v I the taps39 and 4G entirely independent from each other; I p I l I In the examples so far described, the resistanceo fan anode surface was used for determining the position, of

I an exciting beam. However the photoemissive cathode I p I layermay: be so designed as to possess a resistance which;

wFig; 12 shows such an arrangement comprising a pendent from I each other.

i I Fig. 13 shows a system similar to that v v i the difference that, in this instance, the cathode I I In this arrangement a transparent cathode 48, the emissive layer of which possesses a resistance that is not negligible, is provided with two taps 49 and 50 arranged facing an opaque anode 29 whose taps 9 and 10 are located on a straight line perpendicular to the line determined by the cathode taps 49 and 50.

When an exciting beam E breaks through the transparent cathode 48 as at 51, the position of point 51 relative to the taps 49 and 50 is determined in the manner above stated, whereas the zone 52 for catching the electrons emitted by the cathode 48 is localised relative to the taps 9 and 10, like the preceding examples.

The arrangement above described may be used in the most various applications for determining movements of a luminous beam whatever may be the manner in which these movements are effected. In Fig. 4, it was assumed that the shifting of the luminous beam with respect to the tap points of the cell was caused by a rotational movement of a mirror 19, but it is obvious that this relative shifting may be obtained in any other suitable manner, for instance by a movement of the cell, the exciting beam remaining stationary.

The device, according to the invention may be designed with a pure electronic current cell, that is to say with a high vacuum cell, which provides for a constant electric current and whereby a great accuracy. On the other hand, all the electrons emitted by the cathode are caught by the anode whatever may be the position of the impact pointof the 'exciting beam, a condition which secures a great precision.

The device, according to theinvention, may also be designed with barrier layer cells. To this aim, it is suflicient that the film or electron collecting metallic plate have a suitable resistance and that it be provided,

cathode 42 the emissive layer of: which possesses a .re- I I sistance which is not negligible, this layer being provided with two opposite current taps 43 and 44,. Facing I this cathode is arranged an anode 2 which: is of the type v v illustratedv in Figst l and 2., the current taps 9 and 10 at I I I I which, however are located on a straight line at right y angles to the line determined :by the cathode gtaps I 43; v v and-44.-,--. gv beam .E breaks through the transparent I anode 2 and strikes upon the cathode. 42; as at; 45, thus v v v I --:giving rise .to the emission of an electronic beam 46 I I I caught by the anode 2 as in 47; The; position of. the v impact point 45 relative: to the cathode; current; tapping x v v I i points 43- and 44 maybe determined in the above ,de- I I I 1 scribed manner due to the resistance of the emissivelayer I of the] cathode 42, whereas the position of; the catching I v 1 zone 47 relative to the taps 9 and 10 atright angles to I I the taps 43 and44 is also determined in' themanner. dis-v elosedwith reference rto= the preceeding 16Xampi6S.;iIB-. -this-manner,:the. position of the exciting beam may also I p 1 l bedetermined according to two directions at right-angles to each other, the electrical circuitsand thecharacteristics I 1 v ass'ociated with. these two directions being again indeforninstance, with two or four taps, according to the application contemplated. I I k The independence of the characteristic curves corresponding to two perpendicular directions may be obtained by means of an arrangement similar to that herein above described and embodying the combination of two barrier layer'cells, one of which has a front boundary layer and'the other a back boundary layer, each boundary layer having two taps, the semi-conductor being connected in sandwich.

iThe conductivity cells may also be used in a device according to the invention.

In the case of a cathodic oscillograph, the screen itself may be designed for instance according to Figs. 5 or St: and may be used in an arrangement according to the invention.

Of course, the embodiments above described and illustrated in the drawings are given merely as non-restrictive examples, and the shape, the nature, the arrangement and the wiring of their elements, may be modified in any suitable manner without departing from the scope of the invention. It is again pointed out that the invention is also applicable in the case where the current tapping points consist of two or four sets of two lines mutually facing each other.

What we claim is: 1. In an apparatus for determining the relative position of a luminous beam impinging on a photo-electric device, in combination, at least one photo-emissive cathode member having a conductive surface portion adapted to receive a light beam impinging thereon; an anode member having at least one conductive electron collecting surface portion spaced from said surface portion of said cathode member; at least one of said members being light permeable; at least one of said members having at least one pair of conductive, diametrically opposite edge portions conductively connected with said conductive surface portion of the particular member; at least one pair of circuit means, each means of said pair of circuit means being connected to one of said opposite edge portions and being maintained at the same potential as the other; and indicating means for indicating any difference between the amounts of current flowing respectively through said means constituting said pair of circuit means when a beam of light is caused to impinge on said photo-emissive surface portion, such current difierence being a measure of the location of the impinging point of said beam on at least one of said surface portions between said edge portions.

2. An apparatus as set forth in claim 1, including one light-permeable anode member having two opposite conductive surface portions, and two photoemissive cathode members, each having a photo-emissive surface portion facing one of said conductive surface portions of said anode member.

3. An apparatus as set forth in claim 2, including two pairs of said circuit means, the means forming one such pair of circuit means being respectively connected to one pair of said opposite edge regions, the means forming the other pair of circuit means being respectively connected to another pair of said opposite edge regions.

4. An apparatus as set forth in claim 3, wherein said pairs of edge regions are so arranged relatively to each other that a line connecting said opposite edge regions of said one of said pairs intersects a line connecting said opposite edge regions of said other pair so that said lines constitute the axes of a coordinate system and measured current difierences appearing in the respective pairs of circuit means indicate the location of said beam in terms of coordinates relative to said axes.

5. An apparatus as set forth in claim 1 including at least one pair of equal series resistors included in each of said circuit means, respectively, a potential source having a positive and a negative terminal, said positive terminal being connected respectively across said resistors to at least one pair .of'said circuit means respectively connected to said opposite edge regions, said negative terminal being directly connected to said conductive photoemissive surface portion, and said indicating means being connected incircuit between said opposite edge portions in parallel wtih said conductive collecting anode surface portion so that said-circuit means including said resistors constitute two arms of a Wheatstone bridge, while said conductive collecting anode surface portion, being subdivided by the impingement point of said beam into two areas of resistivity terminated by said edge regions, constitutes the other two arms of said bridge, and said indicating means being arranged in the diagonal thereof.

6. An apparatus as set forth in claim 1, including two pairs of said circuit means, the means forming one such pair of circuit means being respectively connected to one pair of said opposite edge regions, the means forming the other pair of circuit means being respectively connected to the other pair of said opposite edge regions, further including two sets of pairedly equal series resistors, one resistor of each set being respectively included in said circuit means of each of said pairs of circuit means, a potential source having a positive and a negative terminal, said positive terminal being connected respectively across said resistors to said pairs of said opposite edge regions of said collecting member, said negative terminal being directly connected to said conductive emitting surface portion, and first indicating means being connected in circuit between said one pair of opposite edge regions in parallel with said conductive collecting surface portion, and second indicating means being connected in circuit between said other pair of opposite edge regions in parallel with said conductive collecting surface portion, so that said one pair of circuit means including one set of said resistors constitutes two arms of a first Wheatstone bridge, while said conductive collecting surface portion, being subdivided by the impingement point of said beam into two areas of resistivity terminated by said one pair of opposite edge regions, constitutes the other two arms of said first bridge, said first indicating means being arranged in the diagonal thereof, and that said other pair of circuit means including the other set of said resistors constitutes two arms of a second Wheatstone bridge, while said conductive collecting surface portion, being subdivided by the impinge ment point of said beam into two areas of resistivity terminated by said other pair of opposite edge regions, constitutes the other two arms of said second bridge, said second indicating means being arranged in the diagonal thereof.

7. An apparatus as set forth in claim 1, including an at least partly evacuated enclosure means, said members being surrounded by said enclosure means.

8. An apparatus as set forth in claim 7, wherein said enclosure means comprises a screen member responsive to cathodic rays emitted from said emitting member, said screen member constituting said collecting anode member of said apparatus.

9. An apparatus as set forth in claim 1, wherein said photoemissive member is formed as a first conductor member, and said collecting anode member is formed as a second conductor, a layer of photo-sensitive material being interposed between, and in contact with, said first and second member, so that said members and said layer constitute a barrier photocell.

10. An apparatus as set forth in claim 1, wherein said photoemissive cathode member is formed as a first conductor member, and said collecting anode member is formed as a second conductor member, a layer of photo-conductive material being interposed between, and in contact with, said first and second member so that said members and said layers constitute a photoconductive cell.

(References on following page) References cited: in thafile of thispatent 25231671 Kallmann Apn a; 1944 Imn-E STATES PATENTS 2,238,381 Batchelor p 1 12 2,027,393; MpCreary Jan. 14, L936 gag; gf l 2,060,524 Patterson Nov. 10, 19 36 f at 3. v 2 065 365 Doyle et a1 Dec. 22, 1936 5 2,527,981 Bramley V Oct. 31,1950 2:13-1:892 Iams Oct 4, 1938 2,553,245 Espenschied u, May 115, 1 951 $153,646. S chro ter Apr. 11, 1939 2,600,373 Moore June10, 1952 2,236,222 Smyth Mar. 25, 1941 7 3 ss Dec. 27, 1955 

